Fire-smoke detection and warning apparatus



Aug. 16, 1955 F. s. JENKINS 2,715,720

FIRE-SMOKE DETECTION AND WARNING APPARATUS Filed 001. 25, 1951 2Sheets-Sheet 1 F. s. JENKINS 2,715,720

Aug. 16, 1955 FIRE-SMOKE DETECTION AND WARNING APPARATUS 2 Sheets-Sheet2 Filed Oct. 25, 1951 Zinventor United States Innissit onsDETECTION ANDWARNING APPARATUS "This invention relates in general to apparatus forautomatically detecting the presence of fire and smoke andfor-immediately announcing or warning of the exis tence of the same;moreparticularly the invention contemplates apparatus Which isespecially adapted for detecting the presence of fire or smoke in asingleplace or a plurality of places considerably emote fromthe'location1 where 1 the warning is given.

The'invention contemplates a novel two-wire detectionand warning systemwherein a plurality of detecting or sensing devices may be located atwidely divergent points remote from a central watch orannunciatorstation, the central station having Warning means not only to announcetheexistence of-fire or smoke-but to show the exact location thereof.Indeed, the apparatus of the present invention detects, warns and showsthe location of fire -or smoke within a single area and also detects,warns and shows the location of fire and smoke in a pluralityofareas.

In addition to the warning locating function, the apparatus of thepresent invention contemplates means-for setting into operation ofautomatic fire extinguishing equipment which is alternatively operablewith the operation of a sensing unit.

Further, the invention contemplates apparatus that is unusuallysensitive, indeed, the sensitivity is so keen that a thin wisp of smokewill cause operation of the Warning mechanism. Furthermore, theequipment of the present invention is very stable andproper operationthereof is substantially independent of ordinary voltage fluctuationsand phase shifting in both urban and rural commercial power systems.

"Furthermore, the apparatus of theinvention provides for the giving ofan immediate alarmLin event of a fault condition,;for example, an openline in the connection between the annunciator and the sensing units.

"The apparatus of thepresent invention is economical indesign for inaccomplishing the above,mentionedfeaturesthe invention contemplatesnovel circuit. means utili in m n mu um se mp n nbkhcnm- .pone m b nda dqmmerqi te ;Th i ve t o o -p ia a vanta a t u t y in st a p ac s tinstance, i lar e mu v t r e War ouse h vin hu flo rea h r pr tect -rquired for mass' concentrations of stocks, equipment, Sup l e a thel hppa a u o th p s vention is particularly usefulin farming. enterprises,for .emmvlem p0 t vtar wh r h vy 9 m yb s tained by the inhalation ofsmoke by the fowl.

The invention is also adaptable for rnilitaryand-naval establishmentshaving greatmasses of personnel inwidely sc e ed barr ck an h spitals anh vin valua equipment and supplies in warehouses and maintenance shops.

In addition, theapparatus of the present invention is capable ofdetecting dust conditions equally-as well as smoke conditions,andtherefore is usable in areas where unusual dust conditions areconsidered a hazard.

atent 0 Furthermore, the invention is nicely adaptable for. use onshipboard, for example, in the holds of merchant vessels.

According to the invention, a warning station or an .annunciator unit iselectrically connected to a single orto a plurality of.detectionorsensing units. .The annunciator performs two functions, namely,warning of the existence of fire or smoke, and also showing the locationofsame. The unit. contemplates mechanism. operative uponactuation ofasingle or a combination of sensing. ,units, whereby audibleand visualmeans;.warn of the existence of the disturbance. .Further, the mechanismof the annunciator is also operative upon actuation of .a single or uponactuation of a combination of'sensing units to show which one or whichcombination of-the units is operative and to thereby show the-location-,of the smoke or fire.

-In the detection scheme of the invention, a sensing unit is connectiblewith the tannunciatornunit asdetermined .by certain control mechanismhaving photoelectric means setting off a fire-etinguishing system.

The controLmechanismfor the sensing unit includes an el ctr d s a tubeha qu bi ng. a rang ment for the grid of the tube which permits a'highdegree of sensitivity, that isto-say, the unit is immediatelyresponsive-to very small changcs in light intensity. The

high-degree of sensitivity is important as it permitsprotectionofilargeareas; i. e. the light sourceand sensing unit may-;be-widely :separated. Also the sensitivity, permits.imrnediatedetection, that is to say, ,warning .of the -fire=whenit; isonlyin thesmoldering stage. In addition,

there ;;is providedcircuit means to;maintain the ratioof the plaie, andgrid voltages substantially constant despite fluctuationjinsupplyvoltage, thus, insuring proper operation during fluctuation in thecommercial powersupply. flfhe ;inv ention permits the use of sensingunits at points ,very remotedfrom each other and from the annunciator.-In connection with this-feature, the system contemplates means forcausing an immediatewarning in the annunciator in-theevent of a fault inthesystem, for-example,

an open line in the annunciator unit, or in the-connection between theannunc-iator and'the several sensing units,

T e;rnanner i n1 which the foregoing featuresareyattain ,d qgether'withthe other advantages of the invention, will be evident from thefollowingdescription, referring to the accompanying drawings, wherein:

;Figure 1 is a-schematic diagram of atypical installat iqn of the apparatus of the present invention;

,Figure 2;is; ;aschematic wiring diagram of the circuit for the lightsource of the-present invention;

"Figure 3- is a schematic wiring diagramof the sensing unit ofthepresent invention; and

Figure '4 is a schematic wiring diagram of the annunciator unit of thepresent invention.

A typical installation of the apparatus of the present invention isshown in Figure 1, a plurality of buildings 1, 111, 11), and 1ceachhaving a sensing unit 1252a, 2b

and-2c andalight source 3, 3a, 3b and 3c. The sensing units areinterconnected to an annunciatorS and to a circuit terminating impedance'6 by lines 7.

Shown connected to annunciator-S are warning devices 5a and-5b whichmaytake the form of'a'horn, siren,

bell or the like. Also shown in the annunciator is warning device 50which warns of the existence of a fire but having a primary purpose ofshowing the location of the fire. The units 4, 4a, 4b and 4c connectedto the sensing units are for the purpose of setting fire extinguishingapparatus into operation.

In the preferred arrangement the operation of the system is as follows.A beam of light 8 from the light source 3 is focused on thephotoelectric element of sensing unit 2. A change in the intensity ofthe beam, for example by the beam being intercepted by fiames, smoke,dust particles or the like, causes actuation of the sensing unit. Aswill be more apparent from the detailed description followinghereinafter, upon actuation of a sensing unit a circuit is establishedbetween elements of the sensand the unit 5c would indicate that both 2and 2c were operative. Indeed, if units, for example 2, 2a and 2b wereto become operative, the annunciator would sound an alarm and indicatethat fire was present in the 1ocation of the operative sensing units.

In passing it is to be observed that the invention permits the use of aplurality of sensing units with the annunciator unit and that thisarrangement is accomplished in a two-wire system. For reasons more fullybrought out hereinafter, the annunciator may be separated from a sensingunit, for example sensing unit 2, by distances up to twenty miles.

From the foregoing, therefore, certain important features of the presentinvention are evident, namely that the invention gives a system for theimmediate detection, warning and indicating the exact location of adisturbance such as fire or smoke in either a single or a combination ofareas and acomplishing this over a two-wire system.

The operation of the line fault Warning arrangement is as follows. Asseen in Figure 1, the impedance 6 is connected to annunciator 5 by wayof line 7. This circuit is continuously energized; thus, if the lineshould be opened, for example at point X, the circuit would becomedeenergized and by means more fully described hereinafter, warningdevice 5b is immediately brought into play. This feature of the presentinvention is very important for quite clearly if the line at X were openand the sensing unit became operative, the annunciator could not warn ofthe existence of the fire or smoke.

Having in mind the foregoing remarks, the details of the structure andoperation of a preferred embodiment of the present invention will bereadily understood from the description following:

The circuit for the light unit 3 shown in Figure 2 includes anincandescent element 9 and a variable resistor 10 and a constant voltagetransformer 11. The transformer is adapted to be connected to a powersource, for example, the ordinary commercial power system, through theterminals 12 of primary winding 11a. The purpose of variable resistor 10is for adjusting the desired light intensity. For example, the intensityrequired where the distance between the light source and the sensingunit is small is less than is required where the distance between theseunits is great. Also, the resistor permits adjustment to the minimumrequired intensity, thus aiding in prolonged life of the incandescentelement.

A constant voltage source for the incandescent element is an importantpart of the invention. As has been mentioned heretofore, the sensingunit is very sensitive to small changes in light intensity, andvariations in light If sensing unit intensity due to voltagefluctuations in the power system would clearly be undesirable. Althoughthe constant voltage means may take a variety of forms, I prefer to usethe transformer type because it gives a high degree of stability and isrugged, sturdy and economical.

The circuit diagram for the preferred form of a sensing unit of thepresent invention is shown in Figure 3. As has been mentionedheretofore, when the unit becomes operative (by interception of thelight beam) it is connected to the lines 7 to thereby establish acircuit with the annunciator unit. This circuit becomes energized, i.e., there is a flow of current in the circuit which operates thewarning-locating mechanism in the annunciator. Since a plurality ofsensing units are used each unit or each combination of units causes adifferent amount of current flow to which the warning locating mechanismin the annunciator circuit accordingiy responds. For the sake ofdescription the current will be referred to as the detection current.

The mechanism in the annunciator unit operative upon the flow of theabove mentioned detection current will be described later. The means forconnecting the unit in the circuit and for determining the amount ofdetection current is described following.

Terminals 14a and 14!; are connected to lines 7 (Figures l and 3) andare also connected to a circuit comprising variable resistor 15,normally open contacts or switch 16, and four-pole double throw switch17. As is clearly shown in Figure 3 the switch 17 is alternativelyoperable in positions 17a and 17b. In either of these positions aclosure of switch 17 connects the circuit with lines 7, hence with theannunciator. The amount of detection current may be regulated by thevariable resistor 15. Thus in an installation such as shown in Figure 1the variable resistor of each unit would be adjusted so that uponclosure of the contacts 16 a different detection current would flow. Aswill later be described, warning-locating mechanism in the annunciatoris made to respond to these different currents or to any combination ofcurrents.

When the switch is in position 171) relay coil 18 is connected in thecircuit. Closure of contacts or switch 16 energizes the coil to closecontacts 18a, thus effectively energizing circuit 19 to set off fireextinguishing equipment. Although the means for alternatively energizinga circuit for setting off fire extinguishing equipment may take avariety of forms, the arrangement I have described is preferred as itrequires a minimum of standard items.

The means for controlling the operation of switch or contacts 16 is animportant part of the invention because in these means a high degree ofstability and sensitivity is obtained. Stability is important so thatthe unit may properly operate despite voltage fluctuation of the powersupply. Sensitivity is important for immediate detection of fire and forprotection of large areas.

Actuation of the switch 16 is accomplished by means of relay 20, theoperation of which is controlled by vacuum tube 21. The coil 20a of therelay is normally energized and by a movable plunger (not shown) holdsthe switch in a normally open position. The switch closes when there isnot sufficient current through the coil to hold in open position.Condenser 20b is shunted across the coil and serves to prevent chatterin the relay. The tube 21 is normally conducting and current flowtherethrough is controlled by the bias on grid 21c. It is by the biasmeans that the high degree of sensitivity of the sensing unit isobtained. The bias is accomplished by a circuit generally indicated bynumeral 22 and photo tube 23.

How the above is accomplished will be apparent with a description of thecircuit.

Power, for example, v. commercial power, is supplied by way of terminals13a and 13b. Transformer 27 is connected across the terminals and theterminals are connected to heater 21d of tube 21. I prefer to operatethe sensing units on D. C. because it helps to reduce relay chatter andthe circuit is not affected by power line disturbance such as phaseshifting. Therefore, halfwave rectifier 2 8 is connected to terminal13a. Resistor 29 is connected inseries with the rectifier and itservesas a current limiting resistor-in the event of short circuit within thesensing unit. Capacitor 30 connected across the input smoothes out theripple of the half-wave rectifier.

Positive terminal-26av of input resistor 26 is connected directly to theanode 23a of photo-tube 23. Tap 26b is connected directly-to cathode 21bof tube 21. Poten tiometer 25 is connected in parallel with the lowerpart of resistor2 6; terminals 25a and 25c being respectively connectedtoterminals 26b and 260. Terminal 25a is also connected to cathode 21b.The movable arm 25b is connected in series withresistor .24 which isconnected with both the grid 210 of tube 21 and the cathode 23b ofphototube 23.

As mentioned heretofore, the tube 21 is normally conducting to energizerelay 20 and hold open switch 16. It is important therefore that powersupply voltage fluctuation does-not affect the tube current flow. Aswill beapparent from an inspectionof the circuit, the potentials makingup the plate to cathode and grid to cathode voltages will changesubstantially proportionately with change in supply voltage. Thus theratio of the plate to cathode andgrid to cathode voltage willrem-ainsubstantially constant to insure substantially constant current flowthrough the tube. Indeed, l have found the unit to be satisfactorilystable with input voltages from 50 to l50volts.

The grid bias of tube 21 determines the sensitivity of the sensing unit.The bias arrangement comprising circuit 22 and tube ;23 make for sharptrigger-like' action, i. e., a small decrease in light intensity fallingon the tube 23 will immediatelycause tube 21 to cease conducting andde-energize relay 20 whereby switch l6 is closed. As seen in Figure 3,the lower half of resistor 26 is used to supply negative voltage topotentiometer 25. voltage may be varied by positioning arm 25b and isapplied to the grid 210 thru resistor 24. In the arrangement, resistor'26 is about'l0,'00O ohm, potentiometer is substantially greater, beingabout 250,000 ohm, and resistor 24 is quite large, being 18 meg-ohms.

Since the phototube is exposed to'light, i. e., light sensitive cathode23b, the D. C. resistance of the tube is lowered and a positive voltageis applied to the grid 2112. In operation, when the desired intensityfrom the light source is set on the phototube, the potentiometer isadjusted to balance the D. C. voltage from the phototube 23, so that thetube 21 is biased near cut-off. If this balanced condition is disturbed,the tube 21 will cease conducting. The condition will be immediatelyupset with a very small decrease in light intensity on the photoelectrictube since the D. C. resistance of the tube increases, causing a drop inpositive potential and allowing the negative bias to take over and stopthe tube conducting.

The bias arrangement described above makes for a very sensitive unit.Indeed, in the described arrangement the sensitivity is maintained evenwith input voltages from 50150 volts. Although the absolute values ofthe resistors and the potentiometer used may vary depending on circuitparameters, I have found that maintaining a very high relative value offixed resistor 24 is important to good sensitivity. Indeed, I have foundthat the ratio of the absolute value of resistor 24 to the absolutevalue of potentiometer 25 should not be less than 60: 1.

Turning now to Figure 4, the structural details and the operation of theannunciator unit will now be described. Terminals 49a and 4% are for thepurpose of receiving power from a power source, for example, theordinary commercial llO-volt supply system. Constant voltage transformer50 is connected to these terminals and is for This Lil

the purpose of keeping the system stable despite power supply voltagefluctation. In the apparatus of the present invention, I prefer a lowoperating voltage and therefore have provided transformer 51 to reducethe, llO-volt supply ,toa voltage of the order'of25v volts. A voltagelevel ofthis order is-preferredbecause,it-provides adequateoperatingpower-for the various circuits and .is conducive to economy incircuit design. I also prefer 'to operate my system onD. C. because thesystem is then relatively free fromthe effects of power linedisturbances, such-{as phase shifting. Full wave rectifier 52accomplishes this purpose. ,Capacitor 53 is connected with terminals5-2a and 52b of the rectifier and is used to filter out highfrequencytransients. The coils ;54a and 55a of fire alarm relay;5 ,4 and linefault relay 55 are-connected in parallel, one end of each coil-beingconnected to one side of warning unit 5c. The other side of the unit isconnected to terminal 56a. The terminal 56b is interconnected toterminal-5 2 b by wayof variable resistor 57d. The terminals 56a and'56bconnect the annunciator unitwith the line 7, as will be apparent by aninspection of Figure l.

Movable-plungers (not shown) responsive to current flow in the coils 54aan d a are adaptedto actuate relay contacts 54b and 55b. The operationof relay5'54 controls certainfire-smoke alarm circuits, and theoperation of relay;5 5 controls a line-faultalarm circuit. Thesecircuits are described-below.

One side of coil 57a of relay 57 isconnected to power terminal 49]) viaconduc tor 58,and transformer 50. The other end of the coil is connectedto power terminal 49a byway of conductor 60, contacts 54b and -conductor-59. As will be apparent from the figure, closure of the contacts- 54bwill energize the coil 57a.

A-movable plunger tnotshown) which is responsive tocurrentpflow in thecoil 57a is adapted to actuate the contacts 57b :and 57c. Closure of thecontacts 5 7b effectively energizes an alarmcircuit. The alarm circuitincludes terminals 61 and 63, terminal 61 beingconnected to powerterminal 49a by way of conductor 62 and terminali63 being connected toterminal; 64 of contacts 571) by way'of switch-65 and conductor.Terminal 67 of contacts 57b is connected to power terminal 49b by way ofconductor 58 and transformer 50. Awarning device-5a which maybe a horn,siren, bell,,or the like, is connected toterminals 61 and.63.Ordinarily, the warning device Sa is of the high capacity type and, isdesigned to operate from the standard 1l0.-volt commercial supplysystem. The purpose may be to send an audiblealarrn over a large area.

Closure of thelcontacts 57c.also energizes an alarm circuit. The alarmcircuit includes terminals 68 and 72, terminal 68 being connected toterminal 69 of contacts 57c via switch 70 and conductor 71. Terminal 72is connected directly to the secondary winding 73b of transformer 73,and thence to terminal 74 of contacts 570 via conductor 75. A warningdevice 5d may be connected to the circuit terminals 68 and 72. Thewarning device is ordinarily a hell or a buzzer of the low voltage typewhich may serve to make an alarm in the vicinity of the annunciator. Inaddition to the audible warning device 5d, I have provided light 83which is, as will be apparent from an inspection of the circuit, adaptedto be energized simultaneously with warning device 5d. The light ingeneral provides a safety feature, for example, if the device 5d failedto operate, the light would serve to give an alarm.

Closure of the contacts 55b of line fault relay 55 effectively energizesan alarm fault circuit. The alarm fault circuit includes terminals 76and 79, terminal 76 being directly connected to terminal 77 of movablecontacts 55b via conductor 78. Terminal 79 is directly connected to oneside of the secondary of the transformer 73 via conductor 80. Terminal81 of movable contacts 55 is directly connected to the other side of thesecondary of transformer 73 by a conductor 82.

A line fault alarm device b is connected to terminals 76 and 79. Thisdevice may be of the same type as warning device 5d.

As has already been described, the warning devices 5b and 5d areenergized from the secondary 73b of transformer 73. The primary 73a ofthe transformer is connected to power terminals 49a and 4%, as isapparent from the figure. The transformer 73 steps down the 110-voltsupply to an operating voltage of the order of six volts. I prefer touse low voltage type warning devices in the annunciator unit, sincethere is less danger of short circuits and also these units areordinarily less expensive than the high voltage type, thereforepermitting economy in design.

Operation of the line fault alarm is as follows: As will be apparentfrom Figures 1 and 4 impedance 6, which is preferably a resistor, isconnected to lines 7 and the annunciator is also connected to the lines7 by terminals 56a and 562). Power is supplied to this circuit viarectifier 52 and there is a current flow through the parallel connectedrelay coils 54a and 5511, the device 5c, lines 7 and resistor 6, andvariable resistor 57d. The current is of such a value that fire alarmrelay 54 will not pick up but is suflicient to pick up line fault relay55 and hold contacts 55a open. In the event of a fault, for example anopen circuit, the relay 55 will be de-energized resulting in the closureof contacts 55b and operation of line fault alarm 5b.

It is to be observed that the impedance 6 is con nected farthermost fromthe annunciator unit. The location is important because in this mannerthe whole line is protected.

The warning device 5c is preferably a milliammeter. The meter is adaptedso that the circulating current in the above described circuit causesthe meter to read zero. The variable resistor is for adjusting theproper value of the circulating current as determined by the impedanceof the connected lines.

Operation of the alarm-indicating means is described as follows: Asmentioned heretofore when a plurality of sensing units are used thevariable resistor in each is adjusted so that there is a different valueof detection current flowing when one or a combination of units areconnected to the lines 7. Accordingly, warning device is responsive tothese various values of detection current. The detection current followsthe same path through the annunciator as the above mentioned circulationcurrent for a line-fault detection, through lines 7 and through thecircuit in the sensing unit connected to terminals 14:: and 14b.

1 2 Since a sensing unit or a combination of sensing units causes apredetermined value of detection current to flow, the scale 85 ofwarning device or milliammeter 5c is calibrated in terms of sensingunits. The sensing units 2, 2a, 2b, 20 may be called stations 1, 2, 3,4, therefore apper ring on the scale are the individual station numbersand various combinations of station numbers. Thus, in the event unit 2(station 1) became operative, the pointer 86 moves over the scale to thestation 1 calibration, the procedure being the same for any otherstation or any combination. Thus, the existence and location of a fireis automatically and immediately shown.

At the same time warning device 5c is actuated by detection currentflow, relay 54 becomes operative and closes contacts 54b which energizespower relay 57 to close contacts 57b and 57c to energize the above described alarm circuits. The detection current has no effect on theoperation of line fault relay as this relay is already energized.Switches and are provided to cut off the operation of devices 5a and 5dif such is desired.

1 claim:

In automatic smoke detecting and warning apparatus, a sensing unitcomprising: a rectifier; a resistor connected with the rectifier andhaving two end terminals and an intermediate tap; a potentiometerconnected between the tap and one terminal of said resistor, thepotentiometer having a movable arm; an electron tube having at least aplate, a grid and a cathode, the cathode being connected to said tap; anelectromagnet connected between said plate and the other of theterminals of said resistor; a photoelectric tube having an anode and acathode, the anode being connected to the other of the terminals of saidresistor; a second resistor connected between the movable arm of saidpotentiometer and the cathode of said photoelectric tube; and anelectrical connection between said grid and the cathode of saidphotoelectric tube.

Rcfcrcnces Qited in the file of this patent UNITED STATES PATENTS1,229,939 Goldstein June 12, 1917 1,994,768 Holven et a1 Mar. 19, 19352,278,920 Evans et al. Apr. 7, 1942 2,452,942 Lord et al. Nov. 2, 19482,577,973 MacDougall et al. Dec. 11, 1951 2,646,556 Allen July 21, 1953FOREIGN PATENTS 289,934 Germany Jan. 28, 1916

